1. Field of the Invention
This invention relates to waterjets in general and waterjet thrust reversing apparatus in particular.
2. Description of the Prior Art
The following prior art patents depict a cross section of the closest prior art now available to the patentee.
U.S. Pat. No. 454,151 to Bowring describes an apparatus wherein the discharge nozzle is square in cross section without a centerbody or pintle. The square cross section permits diverting the flow with a simple rectangular flapper hinge plate that swings into the flow stream. The apparatus has been used in many prior art devices where moving or diverting any substance is involved, such as water in a waterjet propulsion device.
U.S. Pat. No. 3,834,342 to Schoell describes a device where again, the discharge passages are rectangular in cross section, thereby permitting the use of a hinged-type flapper plate. The jet is diverted by moving the curved flappers into the jet downstream of the nozzle exit which is typical of most thrust vectoring or thrust reversing waterjet devices.
A third U.S. Pat. No. 3,269,663 to Strobl describes mixing and diverting of a primary flow and secondary flow of a by-pass flow gas turbine, the flow is diverted upstream of the nozzle plane by swinging a flat plate from one position to another position which closes the forward thrust passage and opens the diversion passage. To accomplish this with a flapper, a large mixing chamber space is required. This is a low efficiency device in that the velocity head entering the mixing chamber is lost and not recovered when the fluid dumps into the mixing chamber.
The instant invention discharges the waterjet flow forward along the side wall of a watercraft. Additionally, the present invention provides an internal thrust reverser having a lower friction loss than the state-of-the-art typical thrust reverser in that turning of the flow is conducted at low velocities before accelerating the flow to the nozzle exit velocity. The present invention provides internal thrust reversing apparatus which consists of diverting the flow into a collector volute upstream of the nozzle by moving a movable plate into the flow stream and closing the nozzle passage. The flow passes from the collector volute through a fixed duct and is discharged in the forward direction to provide for reverse thrust.